1. Field of the Invention
The present invention relates to a lamp such as a headlight or a fog lamp mainly used for a lighting equipment of a vehicle. More specifically, the present invention relates to a lamp referred to as a projection lamp which adopts a reflecting mirror based on a curve of an ellipse having two focuses, a first focus and a second focus, where a cross sectional shape of light that converges to the second focus is projected in the illumination direction using a projection lens to obtain predetermined light-distribution characteristics of the lamp.
2. Description of the Related Art
FIG. 1 is a diagram that illustrates an exemplified configuration of a conventional lamp 90 referred to as a projector-type lamp. This lamp 90 has a light source 91, an ellipse group reflecting surface 92, and a projection lens 93. The ellipse group reflecting surface 92 includes a spheroidal group reflecting surface, a composite ellipse group reflecting surface, or an ellipse free-form surface. The light source 91 is arranged at a position substantially corresponding to a first focus of the reflecting surface 92. As shown in the figure, a shade 94 may be provided if required. The projection lens 93 is attached on the ellipse group reflecting surface 92 through a lens holder 95. As the lamp 90 is constructed as described above, a light source image generated by converging to a second focus of the reflecting surface 92 is magnified by projection through the projection lens 93, resulting in the generation of illuminating light.
At this time, if the light distribution characteristic, for example which consists of low beams but not high beams, is required, a lower half of light beams converging from the light source 91 to the second focus is covered with the shade 94. Therefore, the light projected from the projection lens 93 has the desired light distribution characteristics without including any high beam.
In the conventional projector-type lamp 90 as constructed above, however, the projection lens 93 which is made of an aspheric lens has a small aperture and a light-emitting area of such a lens 93 is not large. Therefore, there is a problem of poor visibility from an oncoming vehicle, a pedestrian, or the like. In addition, the shade 94 blocks almost half of the amount of light at the time of making a low beam distribution. As a result, there is another problem of lowering the utilization factor of beam with respect to the light source 91.
Furthermore, in the case of the projector-type lamp 90, the projection lens 93 can only be observed from the outside. Although there are some dimensional differences in the projection lenses 93, their designs are substantially the same because of their constructional reasons. In other words, they have no differences in appearance, so that their designs can be poor.